Defective motors are repaired by removing the conductor coils from the magnetic iron core and re-winding the core. The coils are, of course, insulated, and are usually held in place by varnish impregnant, wedges, and end blocks. This material, which consists largely of thermoset resins, must be removed or destroyed in order to remove the coils. The usual practice is to burn out the thermoset resins. Burning, however, produces pollutants, uses energy, and leaves a char which is difficult to remove.
An alternative procedure is to immerse the motor in a stripper composition. Commercial strippers, however, swell the resin without destroying it, and a swelled resin may be no easier to remove than an unswelled resin. Moreover, most strippers attack only one or only a few types of resins. Motors which are turned over to repair shops, however, may contain many different resins. The motor owner may not know what resins are in the motor nor can this information be readily ascertained. Therefore, there is no way of knowing which stripper composition, if any, will be effective on a given motor.